In recent years, there are provided systems that allow a user to post a question message on a computer network via a terminal and similarly allow a user to post an answer message to the question message on the network. Furthermore, in these systems, in addition to a questioner and a respondent, a third person is also allowed to access the question message and the answer message that are posted on the network. There are various questions, and, for example, questions about a traffic condition, such as traffic congestion and a suspension of service, a crowded situation of a shop and a weather condition, are allowed.
Here, in the above-described systems, it is advantageously possible to quickly acquire the latest information at a remote place; however, there is a problem that it is difficult to ensure the reliability of information. That is, any user is basically allowed to answer a posted question message, so a user who cannot have a correct answer is also allowed to post an answer message, and it is difficult for a questioner or a third person to judge whether the answer message is a correct answer. Then, for example, Japanese Patent Application Publication No. 2009-211685 (JP 2009-211685 A) suggests a technique for, at the time of accumulating answer messages posted on a network, also acquiring pieces of positional information about mobile terminals that have transmitted the answer messages and then setting only pieces of answer information, transmitted by the mobile terminals located within a meeting place in which a question is asked in advance, for an accumulation target.